Using Only Link-Local Addressing inside an IPv6 Network
RFC 7404

Internet Engineering Task Force (IETF)                      M. Behringer
Request for Comments: 7404                                     E. Vyncke
Category: Informational                                            Cisco
ISSN: 2070-1721                                            November 2014

        Using Only Link-Local Addressing inside an IPv6 Network

Abstract

   In an IPv6 network, it is possible to use only link-local addresses
   on infrastructure links between routers.  This document discusses the
   advantages and disadvantages of this approach to facilitate the
   decision process for a given network.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7404.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Behringer & Vyncke            Informational                     [Page 1]
RFC 7404                     Link-Local Only               November 2014

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Using Link-Local Addressing on Infrastructure Links . . . . .   2
     2.1.  The Approach  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Advantages  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Caveats . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.4.  Internet Exchange Points  . . . . . . . . . . . . . . . .   6
     2.5.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   4.  Informative References  . . . . . . . . . . . . . . . . . . .   8
   Acknowledgments   . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   An infrastructure link between a set of routers typically does not
   require global or unique local addresses [RFC4193].  Using only link-
   local addressing on such links has a number of advantages; for
   example, routing tables do not need to carry link addressing and can
   therefore be significantly smaller.  This helps to decrease failover
   times in certain routing convergence events.  An interface of a
   router is also not reachable beyond the link boundaries, therefore
   reducing the attack surface.

   This document discusses the advantages and caveats of this approach.

   Note that some traditional techniques used to operate a network, such
   as pinging interfaces or seeing interface information in a
   traceroute, do not work with this approach.  Details are discussed
   below.

   During WG and IETF last call, the technical correctness of the
   document was reviewed; however, debate exists as to whether to
   recommend this technique.  The deployment of this technique is
   appropriate where it is found to be necessary.

2.  Using Link-Local Addressing on Infrastructure Links

   This document discusses the approach of using only link-local
   addresses (LLAs) on all router interfaces on infrastructure links.
   Routers don't typically need to receive packets from hosts or nodes
   outside the network.  For a network operator, there may be reasons to
   use addresses that are greater than link-local scope on
   infrastructure interfaces for certain operational tasks, such as
   pings to an interface or traceroutes across the network.  This
   document discusses such cases and proposes alternative procedures.

Behringer & Vyncke            Informational                     [Page 2]
RFC 7404                     Link-Local Only               November 2014